The present invention relates to measurements in exhaust-gas streams, in particular anemometric measurements, for exhaust-gas recirculation in internal combustion engines.
European Patent EP 0 775 316 B1 discloses a hot-film anemometer.
European patent application publication EP 0 990 674 A2 discloses an exhaust-gas recirculation system.
European patent application publication EP 1 431 718 A2, European patent application No. EP 06 806 497, and International patent application publication WO 2008/000494 disclose anemometric measurement devices, and International patent application publication WO 2008/131890 A2 describes a mounting of an anemometric measurement device in an exhaust-gas recirculation pipe.
Simple measurement devices having low temperature requirements and produced in particular with injection-molded housings are suitable only for temperatures up to approximately 140° C. There, a burn-off process for deposits and soot from sensor elements is not possible, because the thin-film measurement elements possibly must be heated actively to 650° C., in order to burn off deposits, in particular soot. During the measurement phase, the sensors are operated at temperatures above the temperature of the exhaust gas. In this way, a plastic housing of the flow sensor may not become overheated.